Compositions for oxidizing garments and related methods

ABSTRACT

The present invention relates generally to compositions and methods for oxidizing or discoloring garments, such as denim. Another aspect relates to providing a cost-effective and environmentally safe alternative to hazardous bleaching agents, such as potassium permanganate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent application Ser. No. 16/920,513, filed Jul. 3, 2020, entitled “COMPOSITIONS FOR OXIDIZING GARMENTS AND RELATED METHODS,” which claims the benefit of priority to U.S. Provisional Patent Application No. 62/870,223, filed Jul. 3, 2019, entitled “COMPOSITIONS FOR OXIDIZING GARMENTS AND RELATED METHODS,” the entire disclosures of which are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

Potassium permanganate (KMnO₄, CAS #7722-64-7) is a powerful oxidizing agent, and is widely used in the denim industry to perform localized discolorations and to accentuate worn looks on garments. Generally speaking, applications of potassium permanganate (KMnO₄) are performed by preparing aqueous solutions ranging from 1% to 4% w/w of KMnO₄. Once prepared, the solution of KMnO₄ is applied by trained personnel to indigo-dyed denim garments by mean of spraying devices. Due to the toxicity and potential hazards posed by exposure to KMnO₄, these spraying devices are typically integrated into the manufacturing process and require adequate ventilation and suction systems. The denim industry has adopted KMnO₄ as the preferred oxidizing agent for primarily economic reasons. In addition, when applied, KMnO₄ discolors the garment, for instance turning the blue denim to a brown color, which provides visual real-time feedback of the areas of the garment that have been treated with the oxidizer. The use of KMnO₄ was consolidated over the years, becoming the current industry standard for localized bleaching operations.

Other methodologies based on different oxidizers, such as sodium hypochlorite, have not been as widely-accepted by the denim industry mainly because, unlike KMnO₄, the alternatives did not enable clear visualization of the areas of the fabric that have been oxidized. In other words, those alternatives do not immediately discolor the garment, so it isn't readily apparent which portions of the fabric had received the solution. This could lead to uneven application or over-dosage leading to damaged fabric, or batch-to-batch inconsistencies.

Despite the economic incentives to use the modestly priced potassium permanganate as an oxidizing agent, potassium permanganate poses significant eco-toxicological concerns. Indeed, according to the Harmonised Classification and Labelling for Hazardous Substances (ATP13) published by the European Union, potassium permanganate has been deemed very toxic to aquatic life, with long lasting effects. Additionally, the classification provided by companies to European Chemicals Agency (ECHA) in Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulations identifies that potassium permanganate is suspected of damaging fertility or the unborn child and may cause damage to organs through prolonged or repeated exposure.

Recently, under the pressure of various non-governmental organizations, major brands of the denim industry have been searching for alternatives to potassium permanganate. By way of example, industry leaders such as Levi Strauss & Co., have publicly declared that they will no longer develop products obtained with sprayed potassium permanganate. For instance, Levi Strauss & Co stated that its goal is to phase out and totally eliminate the use of potassium permanganate. Levi Strauss, Progress on Commitment to Zero Discharge of Hazardous Chemicals (April 2018), available at https://www.levistrauss.com/wp-content/uploads/2019/03/ZDHC-Progress-Update-2018-1.pdf.

In response to this growing demand, various specialty chemical manufacturers have proposed alternatives to KMnO₄, attempting to gain market share and improve the overall public perception of the industry, in terms of innovation and eco-sustainability. Most of the new proposed systems have been based on solutions of persulfates blended with urea or other activators. However, these solutions require the garments to be treated in special ovens (T=>65° C.) in order to obtain intense bleaches. Moreover, the sprayed solutions are less desirable, where the application of the oxidizer is not clearly visible on garments during the bleaching process. The inability to visualize the application can often translate into over-dosage and result in fabric damage or waste.

By way of example, there is a commercially available product that contains cerium sulfate, which in several circumstances can be used as a substitute for KMnO₄ as a localized bleach on denim garments. However, in order to obtain sufficient bleaching, the product must be sprayed in its pure form without any dilution, or with the addition of sodium persulfate. While the product is effective, the resulting cost per treatment of a single garment poses a barrier to many customers, and has limited the wide-scale acceptance of that product.

Another drawback related to the use of common alternatives to potassium permanganate is represented by an undesirable yellow cast exhibited by indigo-dyed denim fabrics after bleaching treatment. The yellow cast is particularly intense if cerium sulfate or sodium persulfate activated by urea is used as a bleaching agent. Despite the pressures exercised by non-governmental organizations and denim brands, KMnO₄ continues to be the most used agent for discolorations in the denim industry.

Accordingly, there remains a long-felt need for a cost-effective and environmentally safe alternative to potassium permanganate that will meet the criteria for a discoloration agent required by the denim industry, but without the hazardous profile of potassium permanganate.

SUMMARY OF THE INVENTION

The present invention relates generally to compositions and methods for oxidizing or discoloring garments, such as denim. Another aspect relates to providing a cost-effective and environmentally safe alternative to hazardous bleaching agents, such as potassium permanganate.

DETAILED DESCRIPTION OF THE FIGURES

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1 depicts bleaching, expressed in lightness variations (DL*), obtained at different concentrations of oxidizing solutions using de-sized fabric as the reference. DL* values are the average of triplicates. Error bars are the standard deviation.

FIG. 2 depicts yellowing, expressed in blueness-yellowness variations (Db*), obtained at different concentrations of oxidizing solutions using de-sized fabric as the reference. Db* values are the average of triplicates. Error bars are the standard deviation.

FIG. 3 depicts denim samples treated with 2 g/L, 5 g/L, 10 g/L and 30 g/L of KMnO₄ and subsequent removal of manganese oxides with hydroxylamine sulfate.

FIG. 4 depicts samples of denim fabric treated with different concentrations of potassium ferrate (VI) and subsequent removal of iron oxides with oxalic acid.

FIG. 5 depicts fabric samples immediately after treatment with solutions of K₂FeO₄ (increasing concentrations from left to right), before the removal of iron oxides with oxalic acid.

FIG. 6 depicts fabric samples immediately after treatment with solutions of KMnO₄ (increasing concentrations from left to right), before the removal of manganese oxides with hydroxylamine sulfate.

FIG. 7 depicts bleaching, expressed in lightness variations (DL*), obtained at different concentrations of Na₂S₂O₈, with or without post-treatment with K₂FeO₄ (15 w/w).

FIG. 8 compares the characteristics of common oxidizers used for denim bleaching including hazards or risk associated with each oxidizer.

FIG. 9 depicts industrial treatments performed using 20 to 60 g/L of k K₂FeO₄.

FIG. 10 depicts Industrial treatments performed using 20 to 60 g/L of K₂FeO₄.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to novel compositions containing potassium ferrate (VI) (K₂FeO₄, CAS #39469-86-8, 13718-66-6) and methods using these compositions as an oxidizing agent for localized discoloration on garments, such as denim. The present invention has numerous benefits over the widely-used options for bleaching denim, such as potassium permanganate, which has been deemed hazardous and poses significant health and environmental risks.

According to at least one embodiment, the present invention contains potassium ferrate (VI). According to at least one embodiment, the present invention is in a powder-form until it is ready to be used. According to at least one embodiment, the present invention is applied after the application of other chemicals on the fabric. In another embodiment, the present invention is mixed into an aqueous solution prior to application on the garment.

EXAMPLES Example 1 Materials and Methods:

Table 1 contains the materials used throughout the experiment.

TABLE 1 Materials used. Material Supplier Model Lot # Potassium Ferrate (VI) 91% Ningbo Hongda Chemicals — HD191104 Industrial Co., Ltd, China Potassium Permanganate 97% Sigma-Aldrich, USA — MKBW1544V Potassium Hydroxide Ercros, Spain — 180609B010 Hydroxylamine Sulfate BASF, Germany — 79115806D0 Oxalic Acid Brenntag, Italy — 2018L1005589 Fortres GSL Kemin Textiles s.r.l., San Marino — 1901117000 DW16 L Kemin Textiles s.r.l., San Marino — 1902113157 Denim Fabric Candiani, Italy RR7716 Elast. 84579D08 Color: sioux - Finish: crispy Spectrophotometer Datacolor, Switzerland Datacolor 550 — Air-cooled IR dyeing unit Datacolor, Switzerland Ahiba IR ® — Beakers 1000 ml for Ahiba Datacolor, Switzerland — — Beakers 300 ml for Ahiba Datacolor, Switzerland — — Lab stenter Gavazzi, Italy RM/1 — Analytical scale Kern, Germany ADB 200-4

The researchers tested K₂FeO₄ (91% purity) as an alternative to conventional oxidizing agents. The testing was performed on a denim substrate, using the classic indigo-dyed denim fabric “Sioux Crispy” provided by the manufacturer Candiani (Italy).

Denim strips (170×15 cm) were cut along weft yarns (average weight: 91.2 grams, SD: 1.1 grams) and treated in the air-cooled infrared dyeing unit with four beakers of 1000 ml. Each beaker contained a fabric sample with 500 ml of a solution consisting of 1 g/L of DW16LT (an α-amylase based product used to remove the sizing starch) and 1 g/L of Fortres GSL (a dispersing agent used to prevent the re-deposition of indigo) to remove the sizing starch. The temperature was maintained at 50° C. for 20 minutes with a rotation speed of 50 rpm. After the de-sizing treatment, the fabric was rinsed in water at 20° C. for 2 minutes, then dried at room temperature overnight. Next, the dried de-sized fabrics (average weight: 84.1 grams, SD: 0.8 grams) were cut along warp yarns (15×10 cm).

Subsequently, the researchers conducted three different studies (Table 2). In all the studies, bleaching tests were obtained in six sequential steps (degradation of indigo dye with an oxidizing solution; rinse with water to remove the excess of metal oxides; drying; removal of metal oxides; rinse with water to remove residual of chemicals; drying in the lab stenter). In all the studies, the oxidation of indigo (Table 2, step 1) and the removal of metal oxides (Table 2, step 4) were performed using the air-cooled infrared dyeing unit (beakers of 300 ml, one fabric sample for each beaker, 28° C., 10 minutes, rotational speed of 50 rpm).

In all the tests, fabric samples were rinsed with water for 2 minutes immediately after the oxidation process (Table 2, step 2) then dried at 25° C. overnight (Table 2, step 3).

In all the studies, fabric samples were rinsed with water for 2 minutes immediately after the removal of metal oxides (Table 2, step 5), then dried at 30° C. with the lab stenter (Table 2, step 6).

TABLE 2 Steps following the desizing procedure in three different studies. Step sequence Step description 1st study 2nd study 3rd study 1 Oxidizing solution K₂FeO₄ (10, 20, 50, K₂FeO₄ (10, 20, 50, KMn0₄ (2, 5, 10, 30 g/L) 100, 150 g/L) 100, 150 g/L) + 20 g/L NaOH 1N 2 Rinse with water 2 min 2 min 2 min 3 Drying 25° C., overnight 25° C., overnight 25° C., overnight 4 Metal oxide removal Oxalic acid, 10 g/L Oxalic acid, 10 g/L Hydroxylamine sulfate, 4 g/L 5 Rinse with water 2 min 2 min 2 min 6 Drying 30° C. with lab stenter 30° C. with lab stenter 30° C. with lab stenter

In the initial study, each fabric sample was treated with 100 ml of solutions of K₂FeO₄ at different concentrations. Iron oxides were removed from fabric samples with 200 ml of a solution of 10 g/L of oxalic acid.

In a second study, tests with potassium ferrate (VI) were repeated adding 20 g/L of KOH 1N in the oxidizing solution to maximize stability of K₂FeO₄ and to reduce the speed of formation of iron oxide according to the reaction 4 K₂FeO₄+4 H₂O→3 O₂+2 Fe₂O₃+8 KOH.

A third study was conducted to mimic the most common conditions used in the denim industry, using potassium permanganate at different concentrations (2 g/L, 5 g/L, 10 g/L, and 30 g/L). Manganese oxide were successively removed from fabric samples with 200 ml of a solution of 4 g/L of hydroxylamine sulfate.

Results: Measurements of L* (lightness) and b* (blueness) were performed using the spectrophotometer, and results provided by solutions of K₂FeO₄ were compared with those offered by solutions of KMnO₄ at four different concentrations (2 g/L, 5 g/L, 10 g/L 30 g/L). A de-sized fabric was taken as a standard reference to calculate DL* (lightness changes) and Db* (blueness changes) as described in FIG. 1 , FIG. 2 , and Table 3.

TABLE 3 DL* and Db* measurements for different bleaching solutions. DL* Db* (lightness (blueness Oxidizing solution variations) variations) First study (K₂FeO₄) K₂FeO₄ (10 g/L) 5.41 −3.64 K₂FeO₄ (20 g/L) 13.07 −4.67 K₂FeO₄ (50 g/L) 35.33 1.68 K₂FeO₄ (100 g/L) 45.22 5.15 K₂FeO₄ (150 g/L) 48.06 5.27 Second study (K₂FeO₄ + KOH 1N) K₂FeO₄ (10 g/L) + KOH 1N (20 g/L) 2.73 −2.35 K₂FeO₄ (20 g/L) + KOH 1N (20 g/L) 7.06 −4.00 K₂FeO₄ (50 g/L) + KOH 1N (20 g/L) 29.94 −0.90 K₂FeO₄ (100 g/L) + KOH 1N (20 g/L) 47.42 5.99 K₂FeO₄ (150 g/L) + KOH 1N (20 g/L) 48.87 6.90 Third study (KMnO₄) KMnO₄ (2 g/L) 34.35 −4.91 KMnO₄ (5 g/L) 47.04 0.15 KMnO₄ (10 g/L) 60.06 8.74 KMnO₄ (30 g/L) 61.16 11.37

Potassium permanganate used with the typical concentrations adopted in the denim industry (10 to 30 g/L) can perform stronger and faster degradation of indigo compared to potassium ferrate (VI). However, potassium ferrate (VI) allows for control of the bleach intensity (FIG. 4 ). The original blueness of the denim is preserved and Db* values for intense discolorations were comparable to those exhibited by potassium permanganate.

A great advantage of using potassium ferrate (VI) is the instantaneous visual feedback of the areas of denim treated with K₂FeO₄ (FIG. 5 ). The denim quickly acquires an intense brown shade due to the presence of iron oxides on the fabric, mimicking the visual effect produced by MnO₂ after the application of KMnO₄ solutions (FIG. 6 ).

Example 2 Materials and Methods:

Table 4 contains the materials used throughout the experiment.

TABLE 4 Summary of materials used. Material Supplier Model Lot # Potassium Ferrate (VI) 91% Ningbo Hongda Chemicals — HD191104 Industrial Co., Ltd, China Potassium Permanganate Sigma-Aldrich, USA — MKBW1544V Sodium Persulfate Brenntag, Italy — 10000103319 Hydroxylamine Sulfate BASF, Germany — 79115806D0 Oxalic Acid Brenntag, Italy — 2018L1005589 Denim Fabric Candiani, Italy RR7716 Elast. 84579D08 Color: sioux - Finish: crispy Air-cooled IR dyeing unit Datacolor, Switzerland Ahiba IR ® — Ahiba beakers 1000 ml for Datacolor, Switzerland — — Ahiba IR ® Spectrophotometer Datacolor, Switzerland Datacolor 550 — Padding equipment Gavazzi, Italy FL300/E — Lab stenter Gavazzi, Italy RM/1 — Analytical scale Kern, Germany ADB 200-4

The researchers tested sodium persulfate (Na₂S₂O₈ CAS #7775-27-1) as a booster for potassium ferrate. Similarly to K₂FeO₄, sodium persulfate is a strong oxidizing agent that can oxidize indigo, thus causing discolorations on denim fabric. To consider sodium persulfate a booster of K₂FeO₄, the increase of lightness of fabric obtained with the combined use of the two substances should be significantly higher than the sum of lightness changes introduced by the same substances if they were used alone. In a first study, tests were performed on squared samples (15 cm×15 cm) of indigo-dyed denim fabric after the following treatments:

-   -   a. The fabric samples were dipped for 15 seconds in solutions         having different concentrations of sodium persulfate at 20° C.         Immediately after, it was performed a hydro extraction using the         padding equipment. Pick-up was 90%±5%.     -   b. Next, the fabric samples were immersed for 15 seconds in a         solution of 15% w/w of K₂FeO₄. The excess of the solution was         removed from the fabric samples using the padding equipment.         Pick-up was 90%±5%.     -   c. The fabric samples were dried in a Gavazzi, model RM/1, lab         stenter at 35° C. for 4 hours.     -   d. In order to simulate the most common processes that are         adopted in industrial laundries, the bleached samples were         treated in an the air-cooled infrared dyeing unit for 20         minutes, at 40° C., and at 40 rpm with 500 ml of a 10 g/L         solution of oxalic acid (1000 ml beakers).     -   e. After the treatment, the fabric samples were rinsed with         water (25° C., 2 minutes) and dried at room temperature         overnight.

To evaluate the contribution of potassium persulfate, a second study was conducted repeating the steps a. and c. of the first study.

Subsequently, measurements of L* (lightness) and b* (blueness) on the fabric samples were performed using the spectrophotometer. A raw untreated fabric was taken as a standard reference to calculate DL* (lightness changes) and Db* (blueness changes) as described in Table 5 and Table 6.

TABLE 5 DL* and Db* measurements on fabrics of denim pre-treated with solutions having different concentrations of Na₂S₂O₈ and subsequently treated with solution of 15% w/w of K₂FeO₄. Pre-treatment Post treatment DL* (lightness Db* (blueness Conc. of Na₂S₂O₈ Conc. of K₂FeO₄ changes) changes) — 15% w/w 10.79 −3.66 2% w/w 15% w/w 18.82 −2.90 5% w/w 15% w/w 21.04 −2.82 10% w/w 15% w/w 25.13 −2.17 15% w/w 15% w/w 26.59 −2.25 20% w/w 15% w/w 26.82 −2.32

TABLE 6 DL* and Db* measurements on fabrics of denim treated with solutions having different concentrations of Na₂S₂O₈. Concentration of DL* (lightness Db* (blueness Na₂S₂O₈ changes) changes) 2% w/w 0.40 −1.56 5% w/w 1.14 −1.91 10% w/w 1.90 −3.24 15% w/w 2.97 −3.63 20% w/w 3.16 −3.68

Results:

Measurements of L* on denim surface revealed that a pre-treatment with solutions of Na₂S₂O₈ immediately before the application of solutions of K₂FeO₄ can significantly increase the performance of bleaching processes. Negative values of Db* shown in Table 5 confirm that treatments with solutions of K₂FeO₄, with or without pre-treatment with solutions of Na₂S₂O₈, do not affect negatively the blueness of the denim substrate. FIG. 7 and the comparison of DL* values shown in Table 5 and Table 6 indicate that Na₂S₂O₈ can significantly enhance performance of bleaching when used immediately before the application of K₂FeO₄.

Example 3

The researcher performed a series of industrial tests, which were conducted in order to evaluate the viability of conducting bleaching with potassium ferrate (VI) as a replacement for potassium permanganate. The initial set of trials involved five different industrial treatments, in which aqueous solutions of potassium permanganate are traditionally used in the denim industry. Next, the same treatments were performed using an aqueous solution of potassium ferrate (VI) as a replacement for the aqueous solution of potassium permanganate.

FIG. 9 describes the treatments performed using the following different techniques:

-   -   Basic: the most common application which includes spraying the         oxidizer solution in a localized area (for example, around the         knees).     -   Nimbus Z: treatment includes special spraying device connected         to the washing machine. In this specific treatment, the         application of the oxidizer is more uniform and is performed on         multiple garments at the same time.     -   Sky-PP: application where rags were previously soaked with a         solution of the oxidizer. Rags were then inserted into the         washing machine together with the garments to achieve a         non-uniform bleached pattern.

Results:

The results using the potassium ferrate as a replacement were very similar to those obtainable with potassium permanganate.

The second set of industrial tests were performed using existing recipes based on potassium permanganate. FIG. 10 describes the treatments performed adopting the different techniques.

Results:

All tests performed confirmed that potassium ferrate (VI) can substitute potassium permanganate for bleaching operations performed in different treatments, on different garments, and adopting different methodologies.

Accordingly, one aspect of the present invention relates to providing an alternative to potassium permanganate for industrial bleaching operations. FIG. 8 provides a comparison of common oxidizers used in the garment industry to bleach denim, including characteristics and known hazards and risks associated with each agent.

Another benefit of the present invention relates to the ability to visualize the application on the garment, with immediate color change appearing on the fabric. In at least one embodiment, the application of the composition containing potassium ferrate changes the denim from a blue color to brown color where it has been applied. This visual change mirrors the results of denim that has been treated with potassium permanganate. Thus, transitioning from potassium permanganate to potassium ferrate would involve very little additional training of laundry personnel, and addresses the concerns expressed with existing alternatives that are commercially available today.

At least one embodiment of the present invention relates to a composition for discoloring or bleaching a garment comprising an effective amount of potassium ferrate (VI). In at least one embodiment, the potassium ferrate is present at a concentration ranging from about 10 to 150 g/L. In another embodiment, the potassium ferrate is present at a concentration of at least 10 g/L.

At least one embodiment of the present invention relates to compositions and methods for discoloring or bleaching garments, wherein the treated garments include but are not limited to denim. According to at least one embodiment, the garment is indigo-dyed denim.

Another aspect of the present invention relates to providing a composition or methods for discoloring or bleaching garments that is less toxic than potassium permanganate. Another aspect of the present invention relates to providing a composition that has characteristics that are environmentally-friendly compared to potassium permanganate. At least one embodiment of the present invention relates to a composition for discoloring or bleaching garments that does not contain potassium permanganate.

According to at least one embodiment, the garment may be optionally treated with a composition comprising sodium persulfate, which is generally understood as a booster to the process.

According to at least one embodiment, the present invention relates to a composition or method for discoloring or bleaching a garment, wherein the composition is a dry powder. In alternative embodiments, the composition may be an aqueous solution. In embodiments where the composition is a dry powder, the user may be required to add water or another liquid solution to the dry powder prior to treating the garment. According to at least one embodiment, the composition is an aqueous solution that can be sprayed onto the garment.

According to at least one embodiment, the present invention relates to providing a composition and methods for discoloring or bleaching a garment, such as indigo-dyed denim, wherein the garment may be treated to remove metal oxides prior to applying the composition to the garment.

According to at least one embodiment, the garment may be treated locally or the garment may be treated in an industrial process where numerous garments are treated simultaneously.

According to at least one embodiment, the present invention relates to a process for discoloring or bleaching a garment, such as denim, where the composition discolors or brightens the garment upon contact and wherein the user can control the process through visual inspection of the discoloration of the garment.

It should be appreciated that minor dosage and formulation modifications of the composition and the ranges expressed herein may be made and still come within the scope and spirit of the present invention.

Having described the invention with reference to particular compositions, theories of effectiveness, and the like, it will be apparent to those of skill in the art that it is not intended that the invention be limited by such illustrative embodiments or mechanisms, and that modifications can be made without departing from the scope or spirit of the invention, as defined by the appended claims. It is intended that all such obvious modifications and variations be included within the scope of the present invention as defined in the appended claims. The claims are meant to cover the claimed components and steps in any sequence which is effective to meet the objectives there intended, unless the context specifically indicates to the contrary.

The foregoing description has been presented for the purposes of illustration and description. It is not intended to be an exhaustive list or limit the invention to the precise forms disclosed. It is contemplated that other alternative processes and methods obvious to those skilled in the art are considered included in the invention. The description is merely examples of embodiments. It is understood that any other modifications, substitutions, and/or additions may be made, which are within the intended spirit and scope of the disclosure. From the foregoing, it can be seen that the exemplary aspects of the disclosure accomplishes at least all of the intended objectives. 

What is claimed is: 1-25. (canceled)
 26. A kit comprising potassium ferrate (VI), oxalic acid, and instructions for (1) applying potassium ferrate (VI) to a garment in an amount effective to permanently discolor the garment and (2) oxalic acid in an amount effective to remove metal oxide.
 27. The kit of claim 26 further comprising sodium persulfate. 